Vaccination is the process of introducing something – either injected or through the mouth – into the body of organisms – humans and animals – and this something – called antigen – is recognized as “foreign, non self, a stranger” and therefore is considered as an enemy, with a potential harm. Therefore the body will mount a protective defensive response by producing something to fight the invader. That something is called antibodies.
In contrast, prophylaxis is the process or the method of giving medicines or drugs to persons currently healthy but with high probability of being exposed to a disease process in the very near future. A classic example would be volunteer health workers about to join a medical mission to areas infested with mosquitoes. Even two weeks before going, each one is already given Chloroquine tablets once a week, the same dose taken while in the area and taken a few weeks even after leaving the place.
Let me digress to congratulate the people of Baguio for the impressive vaccination rollout rate which sent the entire Philippines scrambling to match the performance; the feat led by our beloved Mayor Benjamin Magalong with his staff, our selfless, hardworking front liners, our LGUs and even the media, particularly this paper, with its past editorial devoted to the health issue.
There are currently 170 studies, researches and clinical trials of COVID-19 vaccines worldwide in varying stages of their development, and to date there are no available commercial vaccines, meaning there are no COVID-19 vaccines which can be readily bought in drugstores, like traditional flu and pneumonia vaccines.
In certain emergencies like a pandemic, EUAs or emergency use authorization provides access to medical products that may be potentially used when there are no adequate, approved cure or remedy, based on best available clinical evidence without waiting for all the evidence that would be needed for final approval and clearance by the FDA-Food and Drug Administration or any official regulatory agency, example EMA, European Medical Agency.
In a smaller scale, would be “compassionate use,” allows companies or organizations to provide their experimental – also called investigational – not yet approved drug, to a select group of seriously ill patients with yet no definite drug to cure them but with the doctors’ strong belief, trust and confidence on the greater benefits that would largely outweigh potential risks.
Sinovac and Sinopharm vaccines have the same conventional platform by which most of the approved vaccines are used worldwide. In general, vaccines from living organisms are most effective but they must be prepared from harmless organisms that are anti-genetically related to the pathogen or microbe the vaccine wants to exert its effects on. Inactivated vaccines are those that have been killed by heat, chemicals and other methods.
The AstraZeneca vaccine from UK, Sputnik V from Gamaleya, Russia, Janssen vaccine from Johnson and Johnson USA, utilize the vector-based platform in the production of their vaccines. The vaccines themselves do not contain the antigen – a modifying virus- adenovirus, one of the viruses that cause common colds which is stripped of its pathogenicity (infectiveness) and is introduced or injected into the person, delivering the genetic code for the antigen – the spike protein on the surface of the COVID-10 virus so that the cells of the person will produce large amounts of that antigen. This leads to a challenge to the person’s immune system, which will now mount a massive reaction in the form of high amounts of antibodies.
Of the three, AstraZeneca vaccine, known in Europe as Vaxzevria, was granted EUA by the World Health Organization, so much so that it was one of the vaccines included in its COVAX program to provide free vaccines to the initially planned 92 low and middle income countries in Africa, South America and Asia, including the Philippines. The enthusiasm and acceptance of the vaccine was dampened by reports of a rare potential risk called capillary leak syndrome (CLS), in which fluids from the blood leak out through the porous wall of the small blood vessels, something found mostly in women less than 50 years old. The pause in its use was lifted when health agencies in some countries allayed fears that the incidence of CLS is very low, and that the benefits are much greater than its risk.
It is worth emphasizing that the Gamaleya vaccine, although it utilized the vector-based platform, modified its production by using another strain of the adenovirus used in the formulation of the AstraZeneca vaccine done with scientists of Oxford University in England. Moreover, microbiologists found that the measles (rubeola) virus and the cowpox virus may also be used in the vector-delivery system for the anti-COVID-19 vaccine production. The entire world watches as the race for the ideal vaccine continues.
Next Week: Nucleic Acid formulated Vaccines